title: Enhancement of Ca2+-dependent outward current in sheep bladder myocytes by evans blue dye.
abstract: Whole-cell and inside-out patch-clamp techniques were used to assess the action of a well-known dye, Evans blue, on membrane currents in bladder isolated smooth muscle cells from sheep. In whole cells Evans blue dose-dependently increased the outward current by up to fivefold. In contrast, Evans blue had no effect on inward Ca2+ current. The effect on outward current was abolished or reduced if the cells were bathed in Ca2+-free solution, iberiotoxin (5 x 10(-8) M), or charybdotoxin (5 x 10(-8) M), but was unaffected by externally applied caffeine (5 mM) or in cells exposed to heparin (1 mg/ml) via the patch pipette. In inside-out patches bathed in a Ca2+ concentration of 5 x 10(-7) M, Evans blue (10(-4) M) increased the open probability of large-conductance (298-pS) Ca2+-dependent K+ channels (BK channels), shifting the half maximal-activation voltage by -70 mV. We conclude that Evans blue dye acts as an opener of BK channels.
authors.affiliation: Department of Physiology, School of Biomedical Science, The Queen's University of Belfast, 97 Lisburn Road, Belfast BT9 7BL, Northern Ireland, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Hollywood
authors.forename: K D
authors.initials: KD
authors.lastname: Cotton
authors.forename: N G
authors.initials: NG
authors.lastname: McHale
authors.forename: K D
authors.initials: KD
authors.lastname: Thornbury
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000187:drug effects; D005070:Evans Blue / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*; D024681:Potassium Channels, Calcium-Activated; D012756:Sheep; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D005070:Evans Blue